Scrap car batteries constitute the largest source of secondary lead in the world. Due to the toxicity of lead as well as the quantity of lead in batteries, scrap batteries must be recycled. Increasingly stringent environmental laws have forced the closure of many smelters that process batteries. The few still operating are faced not only with environmental laws, but also the transportation problems associated with the collection of batteries over a large area. At the present time, hazardous waste laws are complicating the disposal of byproducts (such as furnace slag and waste acid electrolyte), in addition to further complicating the transportation of scrap batteries.
Although, to the best of our knowledge, no commercial battery recyclers are currently using electrochemical processing for treating scrap batteries, it is known to use ammoniacal ammonium sulphate to leach lead sulphate and lead monoxide, allowing metallic lead to be electrowon from the solution. More specifically, Bratt and Pickering, in their paper "Production of Lead via Ammoniacal Ammonium Sulphate Leaching", Met. Trans., 1 (8), 2141-49 (1970), describe what has come to be known as the AAS process. However, Bratt and Pickering do not direct themselves specifically to batteries, nor to the broader problem of dealing with all waste materials from scrap batteries (acid, case materials etc.) in an environmentally friendly process.
The present invention builds on the work of Bratt and Pickering.
Accordingly, it is an object of one aspect of this invention to provide a method and apparatus for processing scrap batteries in such a way as to yield only re-usable products, without generating any hazardous or polluting materials that need to be disposed of.
An object of another aspect of this invention is to provide an efficient and inexpensive method and apparatus for processing scrap batteries amenable to small-scale commercialization.
An object of a further aspect of this invention is to provide a method and apparatus for processing scrap batteries in such a way that the need for pollution control equipment is reduced or eliminated, thus reducing capital cost.